An increase in cardiovascular disease is predicted in association with the aging society. Early detection and treatment of cardiovascular disease are important and a periodic examination of cardiovascular function is needed.
Morbidity of atrial fibrillation in cardiovascular disease is known to increase with aging, and epidemiological studies have shown that its prevalence rapidly increases in over the age of 70, and reached 4 to 8% in the seventies and 10% in the eighties. It has been indicated that patients with atrial fibrillation have a high risk for a left atrial thrombus, which flows out from the heart and occludes cerebral vessels to cause cardioembolic stroke. Accordingly, in recent years, aggressive treatment with anticoagulants for preventing cardioembolic stroke have dramatically improved treatment of cardiogenic brain embolism associated with atrial fibrillation.
On the other hand, the heart rhythm in atrial fibrillation is irregular and often results in tachycardia. Therefore, cardiac output is decreased and cardiac function is worsened. The heart rate control therapy in the irregular heart beat has been performed not to cause deterioration of cardiac function. However, the results of mega-clinical trial have demonstrated that there is no significant differences in life prognosis between the strict rate control group, in which patients have a heart rate of less than 80 beats per minute, and the lenient rate control group, in which patients have a heart rate of less than 110 beats per minutes. Consequently, it has been considered that it is not necessary for patients with atrial fibrillation to be treated on the basis of target heart rate. To date, medical treatment in atrial fibrillation is performed based on patient's complaints such as palpitation, shortness of breath, and general fatigue.
As rapidly increasing an aging population, patients with atrial fibrillation and dementia have similarly increased. Furthermore, it has been reported that risk of dementia in patients with atrial fibrillation was increased approximately 1.4-fold. Therefore, it is considered to be problematic for medical treatment on the basis of only elderly patient's complaints as well as complaints of pediatric patients who cannot appropriately explain symptoms. For these reasons, it has been needed to objectively diagnose, perform medical treatment, and observe response to treatment by using a reasonable index for assessment of cardiac function in atrial fibrillation instead of the therapeutic strategy based on subjective patient's complaints.